Crane boom-out transmitter

ABSTRACT

A crane boom radius transmitter employs a boom radius-toelectric signal converter comprising a movable member made in the form of a screen consisting of two sections, which movable member rotates as the boom angle changes. The screen moves between the coupling cores of an inductively coupled detector and sine-wave generator to produce a signal proportional to the boom inclination. Simultaneously, the cores are arranged to rotate relative to the screen as the boom length changes, thereby causing the output signal of the detector to be proportional to the boom radius.

United States Patent [191 Schedrovitsky et al.

[4 1 Mar. 18, 1975 CRANE BOOM-OUT TRANSMITTER [22] Filed: Jan. 2, 1973[21] Appl. No.: 320,682

[30] Foreign Application Priority Data Dec. 31, 1971 U.S.S.R 1,732,412

[52] US. Cl. 340/267 C, 212/39 A, 235/92 MP, 324/34 PS [51] Int. Cl.G08b 21/00 [58] Field of Search 340/267 C, 282; 212/39 A, 212/39 R;324/34 PS, 34 L; 235/92 MP [56] References Cited UNITED STATES PATENTS3,456,132 7/1969 Dechelotte 340/282 3,638,212 [/1972 Peter et al 340/267C Primary Examiner-Glen R. Swann, ill

[57] ABSTRACT A crane boom radius transmitter employs a boomradius-to-electric signal converter comprising a movable member made inthe form ofa screen consisting of two sections, which movable memberrotates as the boom angle changes. The screen moves between the couplingcores of an inductively coupled detector andsine-wave generator toproduce a signal proportional to the boom inclination. Simultaneously,the cores are arranged to rotate relative to the screen as the boomlength changes, thereby causing the output signal of the detector to beproportional to the boom radius.

4 Claims, 5 Drawing Figures PATENIED MAR I 8 I975 SHEET 1 OF 3PAIENTEDHARI8I975 3,872,458

SHEETZOFS i I I I I I I I I l I I I I I I I l I I I I I I I I I I I I II I I I I L.

' PATENTED 1 819.?5

snmao a CRANE BOOM-OUT TRANSMITTER BACKGROUND OF THE INVENTION Thepresent invention relates generally to instruments effecting positioncontrol of movable elements of various machines and mechanisms, and moreparticularly it relates to a crane boom radius transmitter.

Crane boom radius transmitters operating on the principle ofmechanical-electrical conversion are known in the art.

In the prior art crane boom radius transmitters, the boomradius-to-electric signal converter comprises a movable membermechanically linked to the input shaft of the transmitter, which movablemember rotates as the boom angle changes, and means for converting theangle of rotation of the movable member into an electric signal.

Used as the movable member in the known transmitters is a cam coupledthrough the medium of a leverage to the means for converting the angleof rotation of the movable member into an electric signal, which meansis a potentiometer.

A disadvantage of the prior art crane boom radius transmitters residesin the fact that the accuracy of measurement of the boom radius dependson the condition of the cam, leverage and potentiometer proper which aresusceptible to wear and are not reliable and durable enough.

Another disadvantage inherent in the abovementioned transmitters is thatthey have been designed without any allowance being made for asimultaneous measurement of the boom length and the boom angle, whichsubstantially limits the scope of their application.

Still another disadvantage of the prior art transmitters resides in thefact that a too low level of the potentiometer output signal exists,which necessitates an additional amplification thereof and,consequently, involves superfluous consumption of energy.

A further disadvantage of the prior art transmitters is a limited rangeof measurement of the boom radius due to the imperfection of theleverage.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a crane boom radius transmitter that will ensure high accuracyof measurement within a wide range.

Another object of the invention is to provide such an embodiment of thetransmitter that will permit of simultaneously measuring the boom angleand the boom radius of cargo cranes.

Still another object of the invention is to provide a crane boom radiustransmitter with a low consumption of energy.

With this and other objects in view, the essence of the presentinvention resides in the fact that in a crane boom radius transmitter,the boom radius-to-electric signal converter comprises a movable membermechanically linked to an input shaft of the transmitter, which shaftrotates as the boom angle changes, and means for converting the angle ofrotation of the movable member into an electric signal, and the movablemember is, according to the invention, made in the form of a screenconsisting of two sections each described by a similar compound curve,while the means for converting the angle of rotation of the movablemember into an electric signal comprises a detector and a sinewavegenerator inductively coupled to the detector through the medium of twopairs of windings positioned in cores, the primary winding of each pairbeing incorporated in the generator circuit, the secondary winding ofeach pair being incorporated in the detector circuit, and the cores ofeach pair of windings are magnetically coupled and arranged relative toeach other so that the screen section corresponding to each pair alwaysremains, as the screen rotates, within the working gap betweenrespective cores, thus reversing the inductive coupling of each pair ofwindings and altering the output signal.

It is expedient that in the transmitter both pairs of cores be securedcoaxially to the screen so as to move when the crane boom is extended,thus ensuring measurement of the boom radius as the latter changestogether with the boom angle and boom length.

It is advantageous that both screen sections be made in the form ofdisks.

Both screen sections should be preferably arranged in one plane oppositeto each other in the form of a disk.

It is also preferable that both screen sections be arranged in parallelplanes and oriented in opposite directions in the form of two disks.

Both screen sections may also be made in the form of a helix andsymmetrically arranged on a common axis.

Such an embodiment of the crane boom radius transmitter allows forsubstantially simplifying its design and extending the measurementrange.

Another advantage of the proposed crane boom radius transmitter residesin the possibility of measuring the overall boom radius depending on theboom angle and extension.

Still another advantage of the proposed crane boom radius transmitter isthe low energy consumption at a high level of the output signal.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained ingreater detail with reference to embodiments thereof taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a general cut-away view of a crane boom radius transmitter,according to the invention;

FIG. 2 is a general view of the connection pattern of the crane boomradius transmitter, according to the invention;

FIG. 3 is a circuit diagram of the means for converting the angle ofrotation of the movable member into an electric signal, according to theinvention;

FIG. 4 is a general view of the mechanical part of another embodiment ofthe crane boom radius transmitter, according to the invention; and

FIG. 5 is a general view of the mechanical part of still anotherembodiment of the crane boom radius transmitter, according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT shaft 5 coaxial withthe first input shaft 1 and coupled through a link 6 to a bracket 7rotatable round the axis of the shaft 1. Two pairs of cores 8, 9, 10 and11 are secured to the bracket 7, the cores 8 and 9 forming one pair andbeing so arranged relative to each other and to the section 3 of thescreen 2 so that the section 3 is always within the working gap betweenthe cores 8 and 9. The cores 10 and 11 are in turn arranged relative totheir respective section 4 of the screen 2 so that the section 4 isalways within the working gap between the cores 10 and 11. Ferromagneticshell cores are used as the cores 8, 9, 1 and 11, the cores 8 and 11incorporating primary winding 12 and 13, and the cores 9 andincorporating secondary windings 14 and 15, respectively. The cores 8and 9 represent a magnetic circuit for the respective inductivelycoupled windings 12 and 14, while the cores l0 and 11 perform the samefunction for the inductively coupled windings l3 and 15. The windings12, l3, l4 and 15 together with the cores 8, 9, l0 and 11 constitute thecircuit of means 16 for converting the angle of rotation of the movablemember into an electric signal. The latter means 16 together with thescreen 2 form the boom radius-to electric signal converter. The wholetransmitter is contained in a housing 17 provided with packed supportsfor the input shafts 1 and 5, as well as with power supply leads.

The pattern of connection of the crane boom radius transmitter to acrane boom is shown in FIG. 2.

The first input shaft 1 of the transmitter is coupled to a crane boom 19through the medium of a carrier 18. The second input shfat 5 of thetransmitter is connected, through a transmission mechanism comprising areduction gear 20 and a measuring drum 21 rotated by a wire rope 22, toan extending portion 23 of the boom 19.

The electric circuit of the means for converting the angle of rotationof the movable member into an electric signal is represented in FIG. 3.

The circuit comprises a sine-wave generator 24 using a transistor 25 ina known three-point capacitance circuit. The circuit of the generator 24also includes the primary windings 12 and 13 inductively coupled to thesecondary windings 14 and 15. The latter two form part of the circuit ofa peak detector 26 which circuit also includes two diodes 27, capacitors28 and resistors 29. The peak detector circuit is arranged on the linesof a known differential circuit. Two stabilitrons 30 and 31 are providedat the input of the electric circuit to stabilize the supply voltage,while an emitter follower 32 using a conventional circuit and intendedto match the electric circuit with the following stages, is connected tothe output of the circuit of the peak detector 26. The terminals of aDC. source are marked in the diagram with and and the output signal isobtained at points A and B.

Another embodiment of the mechanical part of the crane boom radiustransmitter of the prpesent invention is shown in FIG. 4. In this case,both sections 3 and 4 of the screen 2 are also made in the form ofdisks, but they are arranged in two parallel planes and their profiles(also described by similar compound curves) are oriented in oppositedirections. In this embodiment, the disks are arranged in an off-setmanner each with an equal eccentricity with respect to the common axisof rotation (shaft 1). Both sections 3 and 4 are secured on the firstinput shaft 1, while the cores 8, 9, 10 and ll 4 are mounted on thebracket7' rotatably round the shaft 1.

FIG. 5 shows still another embodiment of the mechanical part of thecrane boom radius transmitter of the present invention.

In this embodiment, both sections 3 and 4 of the screen 2 are made inthe form of conical helices mounted on a hollow shaft 33- moving alongthe first input shaft 1 and secured thereto by means of a sliding key 34ensuring the movement of the hollow shaft 33 along the input shaft 1.The sections 3 and 4 are described by helicoidal lines of the same senseof rotation with a constant lead but with the vertices of the conesoriented in opposite directions, i.e., the sections 3 and 4 are arrangedsymmetrically on a common axis.

A threaded portion 35 with a pitch equal to the lead of the helicoidalline describing the sections 3 and 4 is provided on the end of thehollow shaft 33. The threaded portion 35 is fitted in a fixed nut 36.The bracket 7" with the cores 8, 9, 10 and 11 mounted thereon, isprovided with a bushing 37 fitted on a threaded portion 38 with a pitchequal to that of the threaded portion 35.

In the latter two embodiments, the mechanical part of the crane boomradius transmitter is connected to the crane boom in a manner similar tothat of the embodiment shown in FIG. 2, and the electric circuit of themeans 16 for converting the angle of rotation of the movable member intoan electric signal (FIG. 1) is the same for all the three embodiments,as shown in FIG. 3.

The crane boom radius transmitter operates as follows.

As the boom 19 (FIG. 2) is lowered or raised, the change of the boomangle is transmitted via the carrier 18 to the first input shaft 1. Thelatter turns, and, in so doing, makes the screen 2 (FIG. 1) turn througha pro- .portional angle. The displacement of the extending portion 23(FIG. 2) of the boom (change of the boom length) is transmitted via thewire rope 22, the measuring drum 21 and the reduction gear 20 to thesecond input shaft 5, turning the latter and, consequently, the bracket7 (FIG. 1), carrying the cores 8, 9, l0 and 11, through an angleproportional to the displacement of the boom. As a result, the screen 2and the pair of the cores 8 and 9 rotate relative to each other throughan angle proportional to the boom radius which depends on the boom angleand length.

According to the embodiment of the mechanical part of the transmitter asshown in FIG. 1, the rotation of the screen 2 and cores 8, 9, 10 and 11relative to each other is possible within as the screen 2 is made in theform of a disk.

As the sections 3 and 4 of the screen 2 are arranged opposite to eachother, the section 3 of the rotating screen 2 goes deeper into and thesecond section 4 comes out to the same extent from the working gapbetween the other two cores l0 and 11, thus reversing the inductivecoupling of each pair of the windings 12, 13, 14 and 15. The sinusoidalvoltage induced in the secondary windings 14 and 15 (FIG. 3) has anamplitude which depends on the position of the screen 2 in the workinggap between the cores 8 and 9 and 10 and 11 respectively; the voltage isthen rectified and smoothed by the detector 26. There appears across theoutput of the detector 26 a rectified and smoothed voltage equal to thedifference of the signals obtained in the secondary windings 14 and 15.The input signal of the crane boom radius transmitter is unidirectional(boom radius is always positive) and, consequently, the output voltagescorresponding to this input signal are of an invariable polarity. Toobtain a more powerful output signal, use is made of th emitter follower32 obtained wherefrom is the useful signal proportional to theboomradius of the boom 19.

The second embodiment of the mechanical part of the transmitter, shownin FIG. 4, enables the operating angle of rotation of the screen 2 to beincreased to 360 as the sections 3 and 4 thereof are arranged inparallel planes. In other respects, the transmitter of this embodimentoperates in a manner similar to the one described above.

The third embodiment of the mechanical part of the transmitter, shown inFIG. 5, enables the screen 2 to rotate through an angle exceeding 360.As the hollow shaft 33 rotates together with the first input shaft 1,the threaded portion 35 of the hollow shaft 33 cooperates with the fixednut 36 to displace the hollow shaft 33 together with the screen sections3 and 4 along the first input shaft 1. Since the thread of the portion35 has a pitch equal to the lead of the helices of the sections 3 and 4,the rotation of the first input shaft 1 directly linked to the measuringdrum 21 (FIG. 2) revolving as the boom 19 is extended, the sections 3and 4 (FIG. 5) of the screen 2 travel in the working gap of both pairsof the cores 8, 9, 10 and 11. While the section 3 gradually enters intothe working gap between the cores 8 and 9, the other section 4 graduallycomes out of the working gap between the cores l and 11. As the secondinput shaft rotates, the bracket 7" does so, together with the cores 8,9, 10 and 11 mounted thereon, across the portion 38 by means of the bush37, at the same time advancing along the hollow shaft 33. As a result,the boom radius of the boom 19 (FIG. 2), varying due to a simultaneouschange of the boom angle and length, can be measured. The means 16(FIG. 1) for converting the angle of rotation of the movable member intoan electric signal operates, in the third embodiment of the mechanicalpart of the transmitter, as it does in the first embodiment thereof.

The proposed crane boom radius transmitter can be used for measuring theboom radius range-of a crane, dependent upon the boom angle and changeof boom length as well as in load-lifting capacity limiting devices andfor determining the position of working members of various machines.

The use of the proposed crane boom radius transmitter allows forsubstantially increasing the accuracy of measurement by eliminating theeffect of friction and plays due to the contactless arrangement of themeans 16 for converting the angle of rotation of the movable member intoan electric signal.

The proposed transmitter is advantageous in that its measurement rangeis substantially extended due the employment of the screen 2 consistingof two sections 3 and 4 made in the form of two disks or two conicalhelices.

Another advantage of the proposed transmitter resides in increasing thelevel of the output signal from 0 to 12 V at a low energy consumption,which is due to the circuit of the detector 26 (FIG. 3) also permittingof substantially increasing the sensitivity of the whole means 16(FIG. 1) for converting the angle of rotation of the movable member intoan electric signal.

Still another advantage of the proposed transmitter is its simplifiedstructure which makes the transmitter easy in manufacture.

What is claimed is:

1. A crane boom radius transmitter comprising: a first input shaftcoupled to a crane boom and rotating the boom angle changes; a secondinput shaft coaxial with said first shaft and mechanically coupled withsaid crane boom and rotating as the boom length changes; a boomradius-to-electric signal converter having a movable member and meansfor converting the angle of rotation of said movable member into anelectric signal, said converter being mechanically linked with saidfirst and second input shafts; said movable member being mechanicallycoupled with said first input shaft and being made in the form of ascreen comprising two sections; said means for converting the angle ofrotation of said movable member into an electric signal coupled to saidscreen and including an inductively coupled detector and a sine-wavegenerator; two pairs of windings positioned in magnetically coupledcores and effecting the inductive coupling between said detector andsaid sine-wave generator; said pair of windings each having a primarywinding incorporated in the circuit of said sine-wave generator and asecondary winding incorporated in the circuit of said detector; saidcores being mechanically linked with said second shaft and movingrelative to said screen when said second shaft is rotated; a firstsection of said screen having a profile defined by a variable radiuscurve and being arranged with regard to said cores of said first pair ofwindings so that said first section is constantly in the working gap ofsaid magnetically coupled cores and, while moving, it alters themagnetic coupling therebetween; a second section of said screen having aprofile defined by said curve of a variable radius and being arrangedrelative to said cores of said second pair of windings such that itconstantly, while moving, is arranged in the working gap of saidmagnetically coupled cores, thereby altering the magnetic couplingtherebetween in an inverse manner to the alteration of the magneticcoupling between said first pair of windings, thus altering saidelectric signal.

2. The transmitter as set forth in claim 1, wherein said sections ofsaid screen are each arranged in one plane opposite each other in theform of disks.

3. The transmitter as set forth in claim 1, wherein both of saidsections of said screen are made in the form of disks arranged inparallel planes with opposite orientations of the profiles thereof.

4. The transmitter as set forth in claim 1, wherein each of saidsections of said screen are made in the form of a spatial helix and arearranged on a common axis symmetrical to one another.

1. A crane boom radius transmitter comprising: a first input shaftcoupled to a crane boom and rotating the boom angle changes; a secondinput shaft coaxial with said first shaft and mechanically coupled withsaid crane boom and rotating as the boom length changes; a boomradius-to-electric signal converter having a movable member and meansfor converting the angle of rotation of said movable member into anelectric signal, said converter being mechanically linked with saidfirst and second input shafts; said movable member being mechanicallycoupled with said first input shaft and being made in the form of ascreen comprising two sections; said means for converting the angle ofrotation of said movable member into an electric signal coupled to saidscreen and including an inductively coupled detector and a sine-wavegenerator; two pairs of windings positioned in magnetically coupledcores and effecting the inductive coupling between said detector andsaid sine-wave generator; said pair of windings each having a primarywinding incorporated in the circuit of said sine-wave generator and asecondary winding incorporated in the circuit of said detector; saidcores being mechanically linked with said second shaft and movingrelative to said screen when said second shaft is rotated; a firstsection of said screen having a profile defined by a variable radiuscurve and being arranged with regard to said cores of said first pair ofwindings so that said first section is constantly in the working gap ofsaid magnetically coupled cores and, while moving, it alters themagnetic coupling therebetween; a second section of said screen having aprofile defined by said curve of a variable radius and being arrangedrelative to said cores of said second pair of windings such that itconstantly, while moving, is arranged in the working gap of saidmagnetically coupled cores, thereby altering the magnetic couplingtherebetweEn in an inverse manner to the alteration of the magneticcoupling between said first pair of windings, thus altering saidelectric signal.
 2. The transmitter as set forth in claim 1, whereinsaid sections of said screen are each arranged in one plane oppositeeach other in the form of disks.
 3. The transmitter as set forth inclaim 1, wherein both of said sections of said screen are made in theform of disks arranged in parallel planes with opposite orientations ofthe profiles thereof.
 4. The transmitter as set forth in claim 1,wherein each of said sections of said screen are made in the form of aspatial helix and are arranged on a common axis symmetrical to oneanother.